Heart valve regurgitation is a condition whereby the heart valve does not seal completely as a result of disease or injury, and may have fatal consequences.
Malfunctioning heart valves have typically been replaced with mechanical or biologic heart valve prostheses using highly invasive open-heart surgery techniques. Whilst there has been some success in developing replacement aortic valve prostheses for delivery via percutaneous catheter-based methods, these techniques have not been particularly successful when applied to mitral valve prostheses.
Mitral valve replacement is firstly made difficult as a result of the anatomy of the mitral valve, and particularly that of the mitral valve annulus in which the mitral valve is leaflets are located. The mitral valve annulus is typically very distorted, and of unpredictable and non-uniform geometries, as compared to the relatively uniform aortic valve annulus. This unpredictable anatomy makes it difficult to design a pre-constructed mitral valve prosthesis that would fit the mitral valve annulus in a satisfactory manner for safe, stable and meticulous deployment.
Further, unlike the aortic valve annulus which is entirely surrounded by muscular tissue, the mitral valve annulus is bounded by muscular tissue on the outer wall only, with the inner side of the mitral valve annulus being bounded by a thin vessel wall which separates the mitral valve annulus and the aortic outflow tract. As a result, the mitral valve annulus cannot be subjected to any significant radial forces, as would be typical with an expanding stent type of valve prosthesis, as such radial forces would tend to collapse the aortic outflow tract, resulting in circulatory collapse with likely fatal consequences. As a result of these difficulties, firm anchoring of a deployed mitral valve prosthesis is currently not readily obtainable.
Mitral valve replacement techniques have also generally advocated removal of the native valve prior to location of the replacement mitral valve prosthesis. This is a technically extremely challenging task associated with the potentially fatal complication of profound mitral regurgitation that may not be adequately addressed by the subsequent valve replacement. The lack of an effective mitral valve may lead to overwhelming hemodynamic instability that may not be tolerated by the already compromised left ventricle and overwhelming pulmonary edema may rapidly result.